Toughening of thermoset green zein resin: A comparison between natural rubber‐based additives and plasticizers

Abstract

Zein-based brittle thermoset green resin was toughened using sorbitol, natural rubber fibers (NRF) and epoxidized natural rubber fibers (ENRF). NRF and ENRF were electrospun directly into zein slurry. Chemical, thermal and mechanical properties of zein resin containing NRF (Zein/NRF) and ENRF (Zein/ENRF) were compared with those of sorbitol-plasticized zein. NRF was found to be immiscible in zein and Zein/NRF resins showed two distinct glass transition temperatures (T g ) whereas Zein/ENRF specimens showed significant increases in both T g and degradation temperature (T d ) due to crosslinking between zein and epoxidized natural rubber (ENR). ENRF was more effective in enhancing fracture toughness of zein than NRF or sorbitol.Increased ENRF loading to 15 wt% showed significant increase in toughness with minimal decreases in strength and Young's modulus. Sorbitol and NRF were unable to improve the toughness of zein resin significantly. Environment-friendly zein/ENRF resin with higher fracture toughness developed in this study would be suitable in many applications including green composites.

Development of Bilayer Biodegradable Composites Containing Cellulose Nanocrystals with Antioxidant Properties

“…The main zein peaks were correlated to zein amides I, II, and III, respectively: (i) peak at 1647 cm −1 associated to C=O stretching vibration band of peptide groups with C-N stretching contributions; (ii) in the range of 1538 cm −1 , characterized by vibrations in the plane of N-H bond of peptide groups; and (iii) in the region of 1242 cm −1 and a set of band between 3100 and 2800 cm −1 , associated with C-H vibrations of CH3 and CH2 groups from fatty acids and side chains from amino acids [34]. Zein peaks at 1041-1237 cm −1 corresponded to C-N stretching and hydroxyl groups were also observed through a broad band with a peak at approximately 3288 cm −1 [35]. The incorporation of quercetin was only evidenced with the appearance of a weak peak at 1199 cm −1 associated to C-O stretching in phenol.…”

“…A new band appeared at approximately 1643 cm −1 and is commonly associated to adsorbed water in cellulose [36,37]. Slight chemical interactions between zein and CNC was evidenced by short displacements of zein band from 1175 to 1167 cm −1 associated to C-N stretching of amine groups [35]. Chemical interactions between zein, quercetin, and CNC could be occurring through hydrogen bonding.…”

Enhancement in mechanical and antimicrobial properties of epoxidized natural rubber via reactive blending with chlorhexidine gluconate

“…2 ). Reaction between epoxy groups with amino groups has also been reported 41 – 43 . The reaction resulted in the formation of covalent bonds linking ENR with the CHG structure, which improved the mechanical properties of the ENR/CHG blends.…”

Fabrication of cellulose/plant oil based flexible epoxy thermoset with excellent UV‐blocking performance

“…[8][9][10] To improve the flexibility of the epoxy thermoset, the introduction of plasticizers into the cured resin was the most used strategy. 11,12 Plant oils are important biomass resources with the advantages of abundance, low cost, and biodegradability, and the unique flexible chains of the plant oils make them become ideal plasticizers. [13][14][15][16] Recently, some researchers have made pioneer efforts to develop a series of bio-based flexible epoxy thermosets derived from plant oil and its derivatives, and these bio-based flexible epoxy thermosets with excellent stretchability (elongation at break above 50%) showed promising applications in building materials, electronics, flexible robotic hand actuators, soft robots, and wearable devices.…”

“…To improve the flexibility of the epoxy thermoset, the introduction of plasticizers into the cured resin was the most used strategy 11,12 . Plant oils are important biomass resources with the advantages of abundance, low cost, and biodegradability, and the unique flexible chains of the plant oils make them become ideal plasticizers 13–16 .…”